1. Field
This disclosure relates generally to wireless communication systems and, more specifically, to techniques for handling service flows in wireless communication systems
2. Related Art
Today, many wireless communication systems are designed using a shared uplink (UL) channel. For example, in the Institute of Electrical and Electronics Engineers (IEEE) 802.16 (commonly known as worldwide interoperability for microwave access (WiMAX)) and third-generation partnership project long-term evolution (3GPP-LTE) compliant architectures, a UL channel is shared and resources may be periodically allocated to individual service flows in the case of delay sensitive (e.g., real-time) applications (e.g., voice over Internet protocol (VoIP) applications). In a WiMAX compliant architecture, dynamic service flows for VoIP packets may be initiated by a subscriber station (SS), e.g., a mobile station (MS). However, known MSs have not generally been capable of initiating dynamic service flows for other types of traffic besides VoIP traffic.
In WiMAX compliant wireless communication systems, a quality of service (QoS) parameter set is defined for each service flow, which is a unidirectional flow of packets between an SS and a serving BS and vice versa. Each service flow has an assigned service flow identification (SFID), which functions as a principal identifier for the service flow between an SS and a serving BS. In WiMAX compliant wireless communication systems, scheduling services represent the data handling mechanisms supported by a medium access control (MAC) scheduler for data transport on a connection. Each connection is associated with a single scheduling service, which is determined by a set of QoS parameters that are managed using, for example, dynamic service addition (DSA) and dynamic service change (DSC) message dialogs. IEEE 802.16e compliant wireless communication systems support a number of different data services. For example, IEEE 802.16e compliant wireless communication systems are designed to support unsolicited grant service (UGS), real-time polling service (rtPS), extended real-time polling service (ertPS), non-real-time polling service (nrtPS), and best effort (BE) service.
UGS is designed to support real-time uplink service flows that transport fixed-sized packets on a periodic basis, such as T1/E1 and voice over Internet protocol (VoIP) without silence suppression. In general, UGS offers fixed-sized grants on a real-time periodic basis, which generally eliminates overhead and latency associated with SS requests and generally assures that grants are available to meet real-time requirements of a flow. The rtPS is designed to support real-time uplink service flows that transport variable size data packets on a periodic basis, e.g., moving picture expert group (MPEG) video. The rtPS offers real-time, periodic, unicast request opportunities that are designed to meet real-time requirements of a service flow while allowing an SS to specify a desired grant size. The ertPS is a scheduling mechanism that builds on the efficiency of both UGS and rtPS. Similar to UGS, in ertPS a BS provides unicast grants in an unsolicited manner, which saves the latency associated with a bandwidth request. However, while UGS allocations are fixed in size, ertPS allocations are dynamically sized. The ertPS is designed to support real-time service flows that generate variable size packets on a periodic basis, such as VoIP services with silence suppression. The nrtPS offers unicast polls on a regular basis, which generally assures that an uplink service flow receives request opportunities, even during network congestion. Finally, the BE grant scheduling type is designed to provide efficient service for best effort traffic in an uplink. As noted above, with the exception of VoIP traffic, in WiMAX compliant wireless communication systems all traffic is assigned a BE QoS, as MSs (as currently designed) are not capable of initiating dynamic service flows for other types of traffic.